Proceedings of the IMC, La Palma, 2012 51 Radio polarization measurement of meteor trail echoes during the 2012 Perseids Sylvain Ranvier, Michel Anciaux, Herv´ e Lamy, Johan De Keyser, Stijn Calders, and Emmanuel Gamby Belgian Institute for Space Aeronomy (BIRA-IASB), 3, avenue Circulaire, B-1180 Brussels, Belgium sylvain.ranvier@aeronomie.be We present radio polarization measurements of meteor trail echoes with a cross-polarized antenna of BRAMS, a network of radio receiving stations using forward scatter techniques to detect and characterize meteors. 1 Introduction When using radio techniques to observe meteors, one way of gaining insights into the physical phenomena that produce the meteor echoes is by analyzing the radio polarization of meteor trail echoes (Billam and Browne, 1956; Sidorov et al., 1965; Cannon, 1986). For example, the time variation of the polarization of meteor echoes can, in principle, provide information about electron densities in the meteor trail as shown by Poulter and Baggaley (1977) and by Jones and Jones (1990). Fur- thermore, the physical phenomena that lead to specific signature of some echoes in the time-frequency domains, such as the multiple-branch echoes, the so-called “ep- silons” (Steyaert, 2012), are still not fully understood. The analysis of the polarization of such echoes can be used to increase our knowledge in this field. The paper is organized as follows. In Section 2, the current and future measurement set-ups are described. In Section 3, time variation of the polarization state for long and multiple-branch echoes is analyzed. In Section 4, conclusions are formulated. 2 Measurement set-up 2.1 Current set-up In this study, the forward scattering technique is used to analyze the meteors. The transmitter is the dedi- cated beacon of the BRAMS (Belgian RAdio Meteor Stations) network (Calders and Lamy, 2012) located in Dourbes, in the south-west of Belgium. The transmit- ting antenna is a crossed dipole with an 8 m × 8m ground plane below, as shown in Figure 1. It emits to- wards the zenith a purely sinusoidal wave that is circu- larly polarized, at a frequency of 49.97 MHz and with a power of 150 W. The receiving station, which is located in Uccle, in the Brussels area (about 90 km away from the beacon), includes a crossed 3-element Yagi antenna (see Figure 2), and, therefore, allows measurements of all polarizations. The antenna is tilted 45 ◦ in elevation and 45 ◦ around its axis. In azimuth, the antenna is pointing in the direction of the beacon. Figure 1 – Transmitting antenna in Dourbes, Belgium. Figure 2 – Receiving antenna in Uccle, Belgium. Ideally, the main lobe of the antenna should be pointing 100 km above the beacon. But, due to the ground effect, when the antenna is tilted 45 ◦ in elevation and around its axis, as shown in Figure 2, the main lobe can be at